Serialize and Deserialize Binary Tree

Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or another computer environment.

Design an algorithm to serialize and deserialize a binary tree. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that a binary tree can be serialized to a string and this string can be deserialized to the original tree structure.

For example, you may serialize the following tree

    1
   / \
  2   3
     / \
    4   5

as “[1,2,3,null,null,4,5]“, just the same as how LeetCode OJ serializes a binary tree. You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself. Note: Do not use class member/global/static variables to store states. Your serialize and deserialize algorithms should be stateless.

Solution:

/**
 * Definition for a binary tree node.
 * public class TreeNode {
 *     int val;
 *     TreeNode left;
 *     TreeNode right;
 *     TreeNode(int x) { val = x; }
 * }
 */
public class Codec {

    // Encodes a tree to a single string.
    public String serialize(TreeNode root) {
        Queue<TreeNode> queue = new LinkedList<>();
        queue.offer(root);
        StringBuilder sb = new StringBuilder();
        while(!queue.isEmpty()){
            TreeNode node = queue.poll();
            if(node==null){
                sb.append("#,");
                continue;
            }
            sb.append(node.val+",");
            queue.offer(node.left);
            queue.offer(node.right);
        }
        return sb.toString();
    }

    // Decodes your encoded data to tree.
    public TreeNode deserialize(String data) {
        String[] ele = data.split(",");
        if(ele[0].equals("#")) return null;
        Queue<TreeNode> queue = new LinkedList<>();
        TreeNode root = new TreeNode(Integer.valueOf(ele[0]));
        queue.offer(root);
        for(int i=1; i<ele.length; i++){
            TreeNode parent = queue.poll();
            if(!ele[i].equals("#")){
                parent.left = new TreeNode(Integer.valueOf(ele[i]));
                queue.offer(parent.left);
            }
            i++;
            if(!ele[i].equals("#")){
                parent.right = new TreeNode(Integer.valueOf(ele[i]));
                queue.offer(parent.right);
            }
        }
        return root;
    }
}

// Your Codec object will be instantiated and called as such:
// Codec codec = new Codec();
// codec.deserialize(codec.serialize(root));